The present invention relates to an automatic charging system for an electric motor vehicle, particularly to the system for discriminating the start-stop condition of an engine mounted on the vehicle and for driving a generator connected to the engine as an auxiliary power source of an electric motor depending on a terminal voltage of a battery and on an illumination intensity of lights.
Recently, attention has been paid to electric automobiles as a new type of a transportation system which do not cause environmental pollution and noise pollution. However, a conventional electric automobile involves problems of long electrical charging time and short traveling distance per one charge of the battery. To mount a battery of large capacity in order to lengthen the travelling distance greatly increases the weight of the automobile and also requires a large space for the battery.
In order to eliminate these defects, a hybrid system in which an engine and the battery are mounted on the automobile has been widely adapted. Such a hybrid system includes a serial hybrid system in which an output of the engine is once converted to an electric energy to drive the electric motor as disclosed, for example, in the Japanese Patent Laid-open Publication No. 55-157901 and a parallel hybrid system in which an output shaft of the engine is connected to the electric motor and a driving mechanism being capable of driving the automobile by either one of the engine or motor as disclosed, for example, in Japanese Patent Laid-open Publication No. 59-63901.
Both the types of serial and parallel hybrid systems involve both advantages and disadvantages.
Thus, for example, the serial hybrid system is superior in low fuel consumption and low environmental pollution because of a suitable steady speed operation regardless of variation of load. Automatic charging of an electric automobile of a serial hybrid system is controlled by detecting only the terminal voltage of the battery and by starting the engine when the terminal voltage falls below a certain constant value and automatically stopping the engine when the terminal voltage increases to a predetermined value.
As described hereinbefore, in view of the characteristic features of the electric automobile which causes no environmental pollution and causes only low noise, the indoor use of the electric automobile as a carrying vehicle has been widely considered. However, the indoor use of the engine may contaminate the indoor environment by engine exhaust gas and is not desirable from the viewpoint of noise. Frequent stopping of the engine operation for avoiding the above problems make the re-starting operation of the engine complicated and causes erroneous operation of the automobile.